The invention under consideration concerns a composite body, in particular a sailing or surfboard.
A surfboard is known from EP 0 064 937 A2, which is produced in the so-called xe2x80x9ctwo-shell mode of construction.xe2x80x9d Here, a knit fabric is first applied on a core made of expanded polystyrene (EPS core). Subsequently, a foaming adhesive mass is applied extensively on the core. The core is then inserted between two preformed shell parts, which are either cemented on their joint or with the supply of heat and pressure, are soldered to one another in a production mold.
From EP 0 069 076, a method is known for the production of a composite body with a plastic-hard foam core and a support layer. The production of the composite body takes place with a two-part casting mold, wherein in a first step, the two casting mold parts are lined with a film, which later forms the surface of the composite body. After pouring in a viscous composition, which forms the support layer of the composite body, the hard foam core is inserted and the mold is closed. Then, the foaming and curing of the support layer take place and subsequently, the finished composite body is released from the mold.
Traditional surfboards, manufactured in series, frequently have a so-called xe2x80x9csandwich structure,xe2x80x9d in which hard foam plates made of plastic (for example, foamed PVC), which are clearly sturdier than the foam core and serve as the xe2x80x9csupport layer,xe2x80x9d are cemented on the underside and the upper side of a foam core made of expanded polystyrene. These hard foam plates, however, can be shaped only to a limited extent. In the boundary area of the foam core, which is curved substantially more than the upper side or underside, the hard foam plates are therefore cut off, since their elasticity is not sufficient for the shaping required here. Such a strong shaping would be possible with a supply of thermal energy, which, however, is very labor-intensive and expensive. For the reinforcement of the boundary area, therefore, the gap between the foam core, a cover film, and the joint edges of the upper and lower hard foam plate is laminated with glass-fiber cloth and resin in the thickness of the hard foam plates or filled out with plastic, such as epoxy resin. The xe2x80x9cunfinished surfboard partxe2x80x9d is coated with a watertight surface skin (for example, made of acrylic rubber-styrene-acrylonitrile copolymer (ASA)). The relatively thick lamination or plastic filling in the boundary area of the surfboard, however, increases the weight and is technically, a weak site.
The goal of the invention under consideration is to create a composite body, in particular a surfboard or a wave-riding board, which, with a simple production, is characterized by a low weight and a high strength.
The basic principle of the invention is to be found in providing the support layer, to be applied on a foam core, with a number of incisions or notches, at least in partial areas of its surface. By means of the incisions or notches, the bending capacity of the support layer is increased, so that it can also be adapted to the contour of the foam core in the more curved areas of the composite body, especially in the boundary area. This makes possible a completely closed sandwich structure with a low weight. The closed structure further increases the rigidity, the breaking resistance, and the service life of the composite body.
Preferably, the incisions or notches are provided on the outsidexe2x80x94that is, on the side turned away from the foam corexe2x80x94of the support layer, so that upon bending the support layer, the incisions open fan-like or notch-like.
As a support layer, a hard foam plate, for example, can be used, which can be easily shaped by making incisions or notches in accordance with the contour of the foam core. For the upper side and the underside, a separate hard foam plate will be used as the support layer, which is cemented in the boundary area of the surfboard, joint to joint, with one another. For the production of a seamless transition, the joint area can be over-laminated with overlapping cloth, for example, a glass-fiber cloth.
On the surface of the unfinished part thus obtained, foaming resin is applied, for example, by spraying. In a known manner, the still xe2x80x9cwetxe2x80x9d unfinished part is placed into a two-part production mold, prepared beforehand, into whose mold halves, the surface skin (the so-called ASA layer) is introduced, and subsequently, it is pressed to form a finished surfboard in one single operation.